The effects of diazepam (Valium) on human memory and cognition will be investigated in a series of experiments. The primary goals are to identify the mechanisms of memory impairment induced by the drug, establish the temporal and dose parameters of the decrement, examine the interaction of diazepam with behavioral tasks and the conditions under which the drug is used, and to study the memory effects of diazepam as it interacts with aging and anxiety. Double-blind procedures will be used to test independent groups of diazepam-treated and placebo subjects. Analysis of the memory decrement produced by the drug will be investigated mainly by the free recall method with manipulations of the rate of presentation, list length, rate of acquisition, rehearsal, organization of the list, familiarity of items, and mode of presentation. Alternative explanatory mechanisms which will be investigated are the levels of processing in memory, limitation on processing capacity, memory scanning, and the roles of arousal, motivation and attention. Other memory tasks, psychomotor performance, and subjective mood-evaluation tests will also be employed to assess changes in cognition during drug administration. The effectiveness of several new procedures to assess cognitive performance will be explored. Dose-response functions of diazepam's effect on memory, possible circadian influence and the effects of chronic administration of the drug on memory will be investigated. The possibility that diazepam may produce state-dependent learning will be considered. Differences among individuals will be examined by comparing diazepam's effects on cognition as found in healthy young volunteers to results from older individuals and highly anxious subjects.